Sewing method and device for same

ABSTRACT

In a first step, a needle pierces into an object to be sewed by reciprocal motion and leaves from the object to be sewed after the tip of the needle has penetrated therethrough. At this time, the needle is placed in a state of being stopped relative to the object to be sewed. In a second step, the needle leaves from the object to be sewed. At this time, the needle is moved relative to the object to be sewed along a sewing direction (sewing line).

TECHNICAL FIELD

The present invention relates to a sewing method for forming stitches in an article to be sewn with a needle and a looper, and to a device for the same.

BACKGROUND ART

In order to create a sense of luxury in the cabin of an automobile, stitching patterns may be sewn (stitched) in an instrument panel. Recently, attempts have been made to perform this sewing with a sewing robot having a sewing machine, which is a sewing mechanism, provided on a tip arm thereof. In such a case, the sewing robot moves the sewing machine along the instrument panel in order to create continuous stiches.

Generally, when sewing, the needle pierces and penetrates through the article to be sewn during the outgoing motion, and withdraws from the article to be sewn during the return motion. During this time, the article to be sewn moves relative to the needle. In a case where the article to be sewn is an instrument panel, the interior material forming the instrument panel is made of thick resin, which has relatively high rigidity. In other words, the needle that moves back and forth in the manner described above receives a pressing force oriented in the movement direction of the instrument panel. Accordingly, there is a concern that the needle that has received this pressing force will bend and experience plastic deformation.

Therefore, it is conceivable to control the timing of the movement of the article to be sewn, as described in JP H03-039187 Y.

SUMMARY OF THE INVENTION

The technology described in JP H03-039187 Y changes the movement amount of cloth, which is an article to be sewn, according to a change in the thickness of the cloth. That is, this technology cannot be applied to an article to be sewn in which the thickness barely changes. Furthermore, it is difficult to support an article to be sewn that is thick and has high rigidity, such as an instrument panel, with a post bed. For these reasons, the technology described in JP H03-039187 Y is not easy to implement for an article to be sewn that is thick or has high rigidity.

Ultimately, when sewing an article to be sewn that is thick or has high rigidity, it is difficult to avoid causing bending (plastic deformation) of the needle. This makes it necessary to frequently exchange the needle, and therefore the cost is significantly increased. Furthermore, even if bending of the needle can be avoided, since the needle moves relative to the instrument panel, there is a positional displacement between the location where the needle starts to pierce the article to be sewn (stitch hole formation start position) and the location where the needle stops being withdrawn from the article to be sewn (stitch hole formation end position). Due to this positional displacement, the area of the openings of the stitch holes increases, which negatively affects the appearance.

The present invention has a main object of providing a sewing method making it possible to realize sewing of aesthetically beautiful stitches at a low cost even when the article to be sewn is thick or has high rigidity.

Another object of the present invention is to provide a sewing device configured to be capable of performing the sewing method described above.

According to one embodiment of the present invention, provided is a sewing method for forming stitches on an article to be sewn, wherein a needle whose tip pierces and withdraws from the article to be sewn and a looper that faces the needle with the article to be sewn therebetween and is housed inside a post bed move in a sewing direction relative to the article to be sewn to form the stitches along a trajectory of the movement, the sewing method comprising: a first step of, in a state where the needle is stopped relative to the article to be sewn on the trajectory of the movement, causing the needle to perform back-and-forth motion in a manner to move toward and away from the article to be sewn, to thereby cause the needle to be withdrawn from the article to be sewn after the needle has pierced the article to be sewn; and a second step of, in a state where the needle has been withdrawn from the article to be sewn, moving the needle relative to the article to be sewn in the sewing direction along the trajectory of the movement.

According to another embodiment of the present invention, provided is a sewing device that forms stitches on an article to be sewn, wherein a needle whose tip pierces and withdraws from the article to be sewn and a looper that faces the needle with the article to be sewn therebetween and is housed inside a post bed move in a sewing direction relative to the article to be sewn to form the stitches along a trajectory of the movement, the sewing device comprising: a casing in which the needle and the post bed housing the looper are provided; a transport device configured to move the casing; and a control section configured to control the transport device, wherein the control section brings the needle and the looper into a state of being stopped relative to the article to be sewn on the trajectory of the movement, and causes the needle to perform back-and-forth motion in a manner to move toward and away from the article to be sewn, to thereby cause the needle to be withdrawn from the article to be sewn after the needle has pierced the article to be sewn, and move the needle and the looper relative to the article to be sewn in the sewing direction along the trajectory of the movement when the needle has been withdrawn from the article to be sewn.

According to the present invention, the needle is stopped relative to the article to be sewn during the back-and-forth motion of the needle, that is, from when the needle has pierced the article to be sewn until when the needle is withdrawn from the article to be sewn, and the needle is then moved along the article to be sewn relative to the article to be sewn, when the needle has been withdrawn from the article to be sewn. Accordingly, the piercing start position and the withdrawal end position of the needle substantially match, and the needle is prevented from being pressed due to the article to be sewn moving relative thereto.

Therefore, the area of the openings of the stitch holes is prevented from becoming large and wide, and plastic deformation of the needle caused by bending is avoided. In other words, it is possible to form aesthetically beautiful stitches, and to reduce the cost by reducing the frequency of replacing the needle.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configurational diagram of a sewing device according to an embodiment of the present invention;

FIG. 2 is a schematic perspective view showing specific examples of an article to be sewn that is to be sewn by the sewing device of FIG. 1, and seating portions used in this sewing;

FIG. 3 is an enlarged perspective view of essential parts in a sewing mechanism and the seating portions of the sewing device of FIG. 1;

FIG. 4 is a schematic perspective view of essential parts showing two loopers housed inside a post bed;

FIG. 5 is an enlarged side view of essential parts showing a state in which needles have entered inside the post bed and threads have been hooked onto hooking claws of the loopers;

FIG. 6 is a schematic flow showing a trajectory along which the needle travels back and forth;

FIG. 7 is a schematic perspective view of essential parts showing a state in which loop portions, which are formed by the needles and the loopers of FIG. 4, are joined together;

FIG. 8 is a schematic flow showing the posture change when the post bed moves from a flat portion to a bent portion;

FIG. 9 is a schematic flow showing another trajectory along which the needle travels back and forth;

FIG. 10 is a graph in which the position of the tip of the needle moving along the trajectory shown in FIG. 9 is plotted; and

FIG. 11 is a graph showing the trajectory of the needle as seen from the article to be sewn.

DESCRIPTION OF THE INVENTION

Preferred embodiments of a sewing method according to the present invention will be presented and described in detail below with reference to the accompanying drawings in connection with a sewing device for implementing the sewing method. In the following description, the terms “up”, “down”, “left”, and “right” corresponds to upward, downward, leftward, and rightward in each drawing, but these directions are merely shown for convenience in order to facilitate understanding, and do not define the directions when actually using the sewing device.

FIG. 1 is a schematic configurational diagram of a sewing device 10 according to the present embodiment. This sewing device 10 includes a holding mechanism 12, a sewing mechanism 14, and a sewing robot 16 serving as a transport device (transport mechanism) that transports the sewing mechanism 14. The sewing mechanism 14 is attached to a tip arm 18 of the sewing robot 16 formed by an articulated robot.

First, a general description of the holding mechanism 12 is provided. The holding mechanism 12 includes a frame 20, a plurality of retracting mechanisms 22 that are supported on the frame 20, and a seating portion 24 provided in each of the retracting mechanisms 22. The frame 20 includes a base plate 28 shaped as a substantially flat plate. A retraction air cylinder 30 forming the retracting mechanism 22 is erected on the base plate 28. Specifically, the retraction air cylinder 30 is supported on the frame 20 in a posture whereby a reciprocation rod 32 faces upward in FIG. 1.

The retracting mechanism 22 includes, in addition to the retraction air cylinder 30, a guide bush 34 and a guide pin 36. The guide bush 34 is fixed near the top end of the frame 20, and a tip of the reciprocation rod 32 is inserted therein in a slidable manner. The bottom end of the guide pin 36 is connected to the top end of the reciprocation rod 32 inside the guide bush 34.

The seating portion 24 is provided at the top end of the guide pin 36. Accordingly, the guide pin 36 and the seating portion 24 move back and forth integrally with the reciprocation rod 32. In other words, each seating portion 24 is capable of moving forward or backward (retracting) individually under the effect of the retracting mechanism 22 in which the seating portion 24 is provided. In FIG. 1, the forward motion corresponds to rising and the backward motion corresponds to lowering.

The plurality of seating portions 24 are arranged in parallel in a sewing direction in which the sewing mechanism 14 performs sewing, that is, along a sewing line L shown in FIG. 2. Seating surfaces 37, which are the top surfaces of the seating portions 24, are provided along the sewing line L and curved with a curvature radius substantially equivalent to the curvature radius of an article to be sewn 100 along the sewing line L. If the article to be sewn 100 is an interior base material 102 and a skin material 104 of an instrument panel, for example, the seating portions 24 are arranged as shown by the dashed lines in FIG. 2. The seating portions 24 sequentially retract as the sewing mechanism 14 approaches, as described further below.

The seating surfaces 37 are formed to have substantially the same shape as the article to be sewn 100, as described above (see FIG. 2 or FIG. 3). As a result, the shape of the article to be sewn 100 placed on the seating surfaces 37 is preserved.

As shown in FIGS. 1 and 3, a plurality of suction holes 38 are formed in each seating portion 24. These suction holes 38 are in communication with a suction pump (not shown in the drawings) via negative pressure flow paths and exhaust pipes 40 inside the seating portions 24. By creating suction via the suction holes 38 under the effect of the suction pump, the seating portions 24 hold by suction the article to be sewn 100 placed on the seating portions 24.

The sewing mechanism 14 includes a casing 50 formed with a lying U shape in a side view. The tip arm 18 of the sewing robot 16 is connected to the front surface of a vertical pillar portion 52 forming this casing 50. Furthermore, a sewing motor 54 is provided on one side surface of the vertical pillar portion 52.

The casing 50 further includes a first lateral pillar portion 56 and a second lateral pillar portion 58 that face each other and extend in the same direction respectively from the bottom end and the top end of the vertical pillar portion 52. The first lateral pillar portion 56, which is on the bottom, is provided with a post bed 60 that extends toward the second lateral pillar portion 58, which is on the top. As shown in detail in FIG. 4, a first looper 62 a and a second looper 62 b are housed inside the post bed 60. A driven gear 66 is interposed between the first looper 62 a and the second looper 62 b. This driven gear 66 forms a drive mechanism together with a rotating shaft of the sewing motor 54 via a timing belt, gear train, or the like inside the casing 50. Accordingly, when the rotating shaft of the sewing motor 54 rotates, the driven gear 66 rotates in a following manner, and the first looper 62 a and the second looper 62 b rotate integrally with this following rotation. The configuration described above is widely known, and therefore detailed drawings and descriptions thereof are omitted.

The first looper 62 a and the second looper 62 b each include a hook-shaped hooking claw 70. The hooking claws 70 respectively hook threads 74 a and 74 b, which pass through respective needle eyes 73 (see FIG. 5) of a first sewing needle 72 a and a second sewing needle 72 b (see FIG. 2 in particular). The top end surface of the post bed 60 is open, and therefore the first sewing needle 72 a and the second sewing needle 72 b can be inserted into or withdrawn from the inside of the post bed 60.

The second lateral pillar portion 58 (see FIG. 1) is provided with a reciprocating hilt 78 that moves back and forth in a manner to move toward and away from the first lateral pillar portion 56. The reciprocating hilt 78 is provided with both the first sewing needle 72 a and the second sewing needle 72 b (both of which are needles) via a needle holder 79. The first sewing needle 72 a and the second sewing needle 72 b perform back-and-forth motion integrally with the reciprocating hilt 78, in accordance with the rotation of the rotating shaft of the sewing motor 54. Since this configuration is also widely known, detailed drawings and descriptions thereof are omitted. The first sewing needle 72 a and the second sewing needle 72 b respectively face the first looper 62 a and the second looper 62 b in the post bed 60 (see FIG. 4).

The needle eyes 73 are formed penetrating respectively through the tips of the first sewing needle 72 a and the second sewing needle 72 b. The threads 74 a and 74 b for forming parallel stitches 112 (see FIG. 2), which are a seam, are drawn out from a thread supplying section such as a bobbin (not shown in the drawings), and the tips of these threads 74 a and 74 b are passed through the needle eyes 73.

In this case, the reciprocating hilt 78 repeatedly performs a simple rising and falling action. Therefore, the trajectory of the back-and-forth motion of each of the first sewing needle 72 a and the second sewing needle 72 b is a linear path, such as shown in FIG. 6. In FIG. 6, the second sewing needle 72 b is at a position overlapping with the first sewing needle 72 a on the side away from the viewer in the plane of the drawing. The same is true in FIG. 9 below.

In the above configuration, the holding mechanism 12, the sewing mechanism 14, and the sewing robot 16 are electrically connected to a control section 90, which is a control means. The sewing robot 16 moves the sewing mechanism 14 at a constant speed along the sewing line L (see FIG. 2) oriented in the sewing direction, under the control of the control section 90. Furthermore, at this time, the posture of the casing 50 is changed to match the shape of the article to be sewn 100 at the sewing position, thereby adjusting the posture of the sewing mechanism 14 such that the first sewing needle 72 a and the second sewing needle 72 b become substantially perpendicular to the sewing position on the article to be sewn 100.

The control section 90 also controls the activating or deactivating of the sewing motor 54.

The sewing device 10 according to the present embodiment is basically configured as described above, and the following is a description of the operational effects thereof in relation to the sewing method according to the present embodiment.

When sewing is performed on the article to be sewn 100, first, as shown in FIGS. 2 and 3, the article to be sewn 100 is placed on the seating portions 24 of the holding mechanism 12, and the suction pump is activated. Consequently, suction is exerted via the suction holes 38, and as a result, the article to be sewn 100 placed on the seating portions 24 is sucked and held in a state of being seated on the seating surfaces 37.

Next, the sewing robot 16 operates suitably under the control of the control section 90 to bring the tip arm 18 near the article to be sewn 100 and, as shown in FIG. 3, position the article to be sewn 100 in a manner to be sandwiched between the post bed 60 (first looper 62 a and second looper 62 b), and the first sewing needle 72 a and the second sewing needle 72 b. In other words, the first looper 62 a and the second looper 62 b, and the first sewing needle 72 a and the second sewing needle 72 b face each other with the article to be sewn 100 therebetween. In this way, by providing the sewing robot 16 that transports the sewing mechanism 14, it becomes easy to transport the sewing mechanism 14 to the vicinity of the article to be sewn 100. The threads 74 a and 74 b are drawn out from the thread supplying section and passed separately through the respective needle eyes 73 of the first sewing needle 72 a and the second sewing needle 72 b.

In FIG. 3 (and the enlarged portion of FIG. 2), a state occurring while the sewing progresses from left to right is shown. As can be understood from FIG. 3, when the post bed 60, the first sewing needle 72 a, and the second sewing needle 72 b reach a location where sewing is performed, the retraction air cylinder 30 forming the retracting mechanism 22 retracts the reciprocation rod 32 and the guide pin 36 to move the seating portion 24 away from the article to be sewn 100. When this retraction occurs, the guide bush 34 guides the reciprocation rod 32 and the guide pin 36.

In accordance with the seating portion 24 moving away from the article to be sewn 100, a clearance occurs between the seating portion 24 and the article to be sewn 100. The post bed 60 enters this clearance. In this way, the sewing device 10 is configured to sequentially retract the seating portions 24 according to the position of the sewing mechanism 14, thereby arranging the post bed 60 on the back side of the article to be sewn 100, and perform sewing. The suction from the suction holes 38 of the seating portion 24 to be retracted is stopped before this retraction.

In a case where the article to be sewn 100 is an instrument panel, the interior base material 102 forming this instrument panel is thick and has relatively high rigidity. Therefore, even when the seating portion 24 is moved away from a portion of the instrument panel, the instrument panel does not experience deformation such as warping at this location.

Next, the control section 90 activates the sewing motor 54. As a result, the reciprocating hilt 78 performs back-and-forth motion in the up-down direction. Obviously, the first sewing needle 72 a and the second sewing needle 72 b held by the needle holder 79 also move back and forth in the up-down direction, integrally with the reciprocating hilt 78. On the other hand, the driven gear 66 (see FIG. 4) rotates in a following manner, and the first looper 62 a and the second looper 62 b rotate integrally and in synchronization with the driven gear 66. The first looper 62 a and the second looper 62 b rotate one time while the first sewing needle 72 a and the second sewing needle 72 b move back and forth one time.

While travelling along the outbound path downward from the back end (top dead center), the first sewing needle 72 a and the second sewing needle 72 b pierce the article to be sewn 100 from the top end surface side thereof as shown in FIGS. 5 and 6, and when reaching the forward end (bottom dead center), the tips of the first sewing needle 72 a and the second sewing needle 72 b protrude from the bottom end surface of the article to be sewn 100 and enter the empty space inside the post bed 60. In accordance with this, the threads 74 a and 74 b penetrate through the article to be sewn 100. After this, the first sewing needle 72 a and the second sewing needle 72 b travel on the return path from the bottom dead center to the top dead center, and are withdrawn from the post bed 60 and the article to be sewn 100 during this travel.

While the first sewing needle 72 a and the second sewing needle 72 b are moving back and forth as described above, each arm of the sewing robot 16 is stopped without pivoting or moving. In other words, the first sewing needle 72 a, the second sewing needle 72 b, and the post bed 60 are stopped relative to the article to be sewn 100. Accordingly, the positions where the first sewing needle 72 a and the second sewing needle 72 b start to pierce the article to be sewn 100 during the outgoing motion substantially match the positions where the withdrawal of the first sewing needle 72 a and the second sewing needle 72 b from the article to be sewn 100 ends during the return motion.

The piercing start positions of the first sewing needle 72 a and the second sewing needle 72 b during the outgoing motion are the positions where the formation of the stitch holes is started. On the other hand, the withdrawal end positions during the return motion are the positions where the formation of the stitch holes ends. Since the piercing start positions and the withdrawal end positions match as described above, the formation start positions and the formation end positions of the stitch holes substantially match. Accordingly, the area of the openings of the stitch holes is prevented from becoming large. Therefore, it is possible to realize the parallel stitches 112 (see FIG. 2) that are aesthetically beautiful.

When the threads 74 a and 74 b have penetrated through the article to be sewn 100 integrally with the tips of the first sewing needle 72 a and the second sewing needle 72 b, the respective hooking claws 70 of the first looper 62 a and the second looper 62 b reach the top dead center. The threads 74 a and 74 b that have penetrated through the article to be sewn 100 are hooked on the hooking claws 70. In this state, the first sewing needle 72 a and the second sewing needle 72 b rise, and the first looper 62 a and the second looper 62 b rotate, whereby the threads 74 a and 74 b are pulled downward in FIGS. 2 and 3. The pulled threads 74 a and 74 b form loop portions 110 shown in FIG. 7 on the bottom end surface side of the article to be sewn 100.

The sewing robot 16 keeps the first sewing needle 72 a and the second sewing needle 72 b stopped relative to the article to be sewn 100, until the rising of the first sewing needle 72 a and the second sewing needle 72 b that have pierced the article to be sewn 100 (that is, the withdrawal of the first sewing needle 72 a and the second sewing needle 72 b from the article to be sewn 100) ends, as described above. Then, upon detecting that the first sewing needle 72 a and the second sewing needle 72 b have been withdrawn from the article to be sewn 100 and are positioned at the top dead center, the control section 90 implements the second step.

Specifically, the control section 90 suitably operates the arm of the sewing robot 16 to slightly move the first sewing needle 72 a, the second sewing needle 72 b, and the post bed 60 along the sewing line L, as shown in FIG. 6. As a result, the first sewing needle 72 a, the second sewing needle 72 b, the first looper 62 a, and the second looper 62 b move in the sewing direction (on the sewing line L) relative to the article to be sewn 100.

Since the first sewing needle 72 a and the second sewing needle 72 b are withdrawn from the article to be sewn 100, the first sewing needle 72 a and the second sewing needle 72 b are not pressed on by the article to be sewn 100 during this movement. Accordingly, the first sewing needle 72 a and the second sewing needle 72 b are effectively prevented from being bent and experiencing plastic deformation. Therefore, the frequency of replacing the first sewing needle 72 a and the second sewing needle 72 b is reduced, and so the cost incurred by such replacement can be reduced.

After this, the first step and the second step described above are repeated. Obviously, the first sewing needle 72 a and the second sewing needle 72 b are stopped relative to the article to be sewn 100 in the first step. Furthermore, the second step (movement of the first sewing needle 72 a and the second sewing needle 72 b relative to the article to be sewn 100) is implemented when the first sewing needle 72 a and the second sewing needle 72 b have been withdrawn from the article to be sewn 100. Accordingly, in a case where sewing is performed continuously, it is possible prevent the area of the openings of the stitch holes from becoming large and to avoid plastic deformation of the first sewing needle 72 a and the second sewing needle 72 b. In other words, according to the present embodiment, it is possible to realize aesthetically beautiful parallel stitches 112 along the movement trajectory of the first sewing needle 72 a and the second sewing needle 72 b, at a low cost.

In particular, in a case where the article to be sewn 100 has flat portions 120 and bent portions 124 such as shown in FIG. 8, the post bed 60 changes its posture when moving from the flat portion 120 to the bent portion 124. This is because the sewing robot 16 changes the posture of the sewing mechanism 14 such that the post bed 60, the first sewing needle 72 a, and the second sewing needle 72 b become substantially perpendicular to the surface of the portion being sewn, according to teaching implemented in advance.

At the flat portion 120 where there is almost no height difference, the post bed 60 contacts or is separated from the back surface of the article to be sewn 100 by only a slight distance. On the other hand, the distance between the article to be sewn 100 and the post bed 60 becomes greater as the post bed 60 approaches the bent portion 124. With the sewing method according to the prior art in which the first sewing needle 72 a and the second sewing needle 72 b are moved along the article to be sewn 100 while performing the back-and-forth motion, when the distance between the article to be sewn 100 and the post bed 60 becomes great, the positional displacement between the piercing start positions and the withdrawal end positions of the first sewing needle 72 a and the second sewing needle 72 b becomes large. This causes an increase in the area of the openings of the stitch holes and negatively affects the aesthetic appearance. Furthermore, there is a concern that the first sewing needle 72 a and the second sewing needle 72 b will be bent.

On the other hand, with the present embodiment, the piercing start positions and the withdrawal end positions substantially match even in a case where the distance between the article to be sewn 100 and the post bed 60 becomes great. This is because the first sewing needle 72 a and the second sewing needle 72 b are stopped relative to the article to be sewn 100 in the first step, as described above. Furthermore, also in such a case, the article to be sewn 100 is relatively moved when the first sewing needle 72 a and the second sewing needle 72 b are withdrawn from the article to be sewn 100, and therefore concern about bending of the first sewing needle 72 a and the second sewing needle 72 b can be eliminated.

Ultimately, in this case as well, it is possible to realize aesthetically beautiful parallel stitches 112 at a low cost.

In the first step, the first sewing needle 72 a and the second sewing needle 72 b may be moved by the operation of the arm of the sewing robot 16, and the article to be sewn 100 may be moved by the same amount in the same direction as the first sewing needle 72 a and the second sewing needle 72 b. In this case as well, the first sewing needle 72 a and the second sewing needle 72 b are in a state of being stopped relative to the article to be sewn 100. Furthermore, in the second step, the article to be sewn 100 may be moved instead of moving the first sewing needle 72 a and the second sewing needle 72 b.

The regions of the threads 74 a and 74 b pulled the next time the first sewing needle 72 a and the second sewing needle 72 b pierce the article to be sewn 100 (the next time the first looper 62 a and the second looper 62 b rotate) are inserted into the loop portions 110 shown in FIG. 7. By repeating the first step and the second step described above, the loop portions 110 are joined to each other to realize the sewing. FIG. 7 shows an example of only the thread 74 a, but it is obvious that the loop portions 110 are joined to each other in the same manner for the thread 74 b as well. On the other hand, the parallel stitches 112 connected linearly are formed on the top end surface side of the article to be sewn 100, as shown in FIG. 2.

The sewing mechanism 14 is moved at a constant speed to the right in FIGS. 2 and 3, for example, by the sewing robot 16. Furthermore, at a location where the sewing has ended and the sewing mechanism 14 has moved away, suction from the suction holes 38 is resumed, and the reciprocation rod 32 and the guide pin 36 rise up while being guided by the guide bush 34 due to the effect of the retracting mechanism 22. As a result, the article to be sewn 100 becomes placed on the seating portions 24.

On the other hand, the seating portion 24 at a position that would interfere with the sewing mechanism 14 that has moved is retracted from the article to be sewn 100 under the effect of the retracting mechanism 22. In other words, after the suction from the suction holes 38 has been stopped, the reciprocation rod 32 is lowered such that the seating portion 24 is retracted to a position where the seating portion 24 does not interfere with the sewing mechanism 14. In this way, the first step and the second step are implemented on a region of the article to be sewn 100 where support by the seating portion 24 has been removed.

When the control section 90 detects that the parallel stitches 112 with a prescribed length have been formed, the operation of the sewing robot 16 is stopped under the control of the control section 90 and the sewing motor 54 is deactivated. Accordingly, the back-and-forth motion of the first sewing needle 72 a and the second sewing needle 72 b and the rotation of the first looper 62 a and the second looper 62 b are stopped. After regions of the threads 74 a and 74 b between the article to be sewn 100 and the first sewing needle 72 a and the second sewing needle 72 b have been cut, the sewing robot 16 operates suitably to move the sewing mechanism 14 away from the article to be sewn 100. Thus, the sewing is ended.

The present invention is not limited to the above-described embodiment, and various modifications can be adopted therein without departing from the essence and gist of the present invention.

For example, as shown in FIGS. 9 and 10, the sewing mechanism may cause the first sewing needle 72 a and the second sewing needle 72 b to perform the back-and-forth motion along elliptical trajectories when viewed from the front surface of the casing 50. Here, FIG. 10 is a graph in which the positions of the tips of the first sewing needle 72 a and the second sewing needle 72 b are plotted. The post bed 60 is stopped relative to the first sewing needle 72 a and the second sewing needle 72 b.

In this case, the article to be sewn 100 is moved along with the movement of the first sewing needle 72 a and the second sewing needle 72 b. When the minor axes of the ellipses traced by the movement trajectories of the first sewing needle 72 a and the second sewing needle 72 b are 2 mm, for example, the article to be sewn 100 may be moved by 2 mm. The movement direction at this time is the same as the direction in which the first sewing needle 72 a and the second sewing needle 72 b move from when the first sewing needle 72 a and the second sewing needle 72 b pierce the article to be sewn 100 to when these needles are withdrawn. For example, in FIG. 9, the first sewing needle 72 a and the second sewing needle 72 b move to the left while performing the back-and-forth motion. Accordingly, the article to be sewn 100 is moved to the left while the first sewing needle 72 a and the second sewing needle 72 b perform the back-and-forth motion.

As a result, even in a case where the first sewing needle 72 a and the second sewing needle 72 b perform the back-and-forth motion along elliptical trajectories, the first sewing needle 72 a and the second sewing needle 72 b are stopped relative to the article to be sewn 100. Accordingly, the piercing start positions and the withdrawal end positions of the first sewing needle 72 a and the second sewing needle 72 b are aligned, as shown in FIG. 11, which shows the trajectories of the first sewing needle 72 a and the second sewing needle 72 b as viewed from the article to be sewn 100. Therefore, it is possible to prevent the area of the opening of each stitch hole from becoming large and to avoid plastic deformation of the first sewing needle 72 a and the second sewing needle 72 b, in the same manner as described above. In other words, it is possible to realize aesthetically beautiful parallel stitches 112 (see FIG. 2) at a low cost.

Furthermore, the number of sewing machine needles and the number of loopers may be one.

Furthermore, the article to be sewn 100 is not limited to being the interior base material 102 and the skin material 104 of the instrument panel for an automobile, and may be any article that can be pierced by a sewing machine needle.

The timing at which the second step is performed is not particularly limited to when the first sewing needle 72 a and the second sewing needle 72 b have reached the top dead center. As an example, the second step may be implemented immediately after the first sewing needle 72 a and the second sewing needle 72 b have withdrawn from the article to be sewn 100.

Yet further, the seating portions 24 may be formed using suction pads. 

What is claim is:
 1. A sewing method for forming stitches on an article to be sewn, wherein a needle whose tip pierces and withdraws from the article to be sewn and a looper that faces the needle with the article to be sewn therebetween and is housed inside a post bed move in a sewing direction relative to the article to be sewn to form the stitches along a trajectory of the movement, the sewing method comprising: a first step of, in a state where the needle is stopped relative to the article to be sewn on the trajectory of the movement, causing the needle to perform back-and-forth motion in a manner to move toward and away from the article to be sewn, to thereby cause the needle to be withdrawn from the article to be sewn after the needle has pierced the article to be sewn; and a second step of, in a state where the needle has been withdrawn from the article to be sewn, moving the needle relative to the article to be sewn in the sewing direction along the trajectory of the movement.
 2. The sewing method according to claim 1, wherein the article to be sewn is positionally fixed, and a trajectory of the back-and-forth motion of the needle in the first step is made linear.
 3. The sewing method according to claim 1, wherein the article to be sewn is moved, and a trajectory of the back-and-forth motion of the needle in the first step is made elliptical.
 4. The sewing method according to claim 1, wherein the first step is performed in a state where the post bed housing the looper is separated from the article to be sewn.
 5. The sewing method according to claim 1, wherein the second step is performed when the needle reaches a top dead center.
 6. A sewing device that forms stitches on an article to be sewn, wherein a needle whose tip pierces and withdraws from the article to be sewn and a looper that faces the needle with the article to be sewn therebetween and is housed inside a post bed move in a sewing direction relative to the article to be sewn to form the stitches along a trajectory of the movement, the sewing device comprising: a casing in which the needle and the post bed housing the looper are provided; a transport device configured to move the casing; and a control section configured to control the transport device, wherein the control section brings the needle and the looper into a state of being stopped relative to the article to be sewn on the trajectory of the movement, and causes the needle to perform back-and-forth motion in a manner to move toward and away from the article to be sewn, to thereby cause the needle to be withdrawn from the article to be sewn after the needle has pierced the article to be sewn, and move the needle and the looper relative to the article to be sewn in the sewing direction along the trajectory of the movement when the needle has been withdrawn from the article to be sewn.
 7. The sewing device according to claim 6, wherein a trajectory of the back-and-forth motion of the needle is linear.
 8. The sewing device according to claim 6, wherein a trajectory of the back-and-forth motion of the needle is elliptical.
 9. The sewing device according to claim 6, wherein in a state where the post bed housing the looper is separated from the article to be sewn, the control section moves the needle and the looper relative to the article to be sewn in the sewing direction along the trajectory of the movement.
 10. The sewing device according to claim 6, wherein when the needle reaches a top dead center, the control section moves the needle and the looper relative to the article to be sewn in the sewing direction along the trajectory of the movement. 